RU2393987C2 - Method of obtaining heavy water-d2 from underground water - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to water production. The method of obtaining heavy water-D₂, consisting of deuterium oxide (D₂O, HDO), with total deuterium content which exceeds deuterium content in ocean water and is characterised by ratio of deuterium to protium D/H ranging from 1: 6420.54 to 1:1950, which corresponds to the range of values δD from 0 to +2300‰ on the Standard Mean Ocean Water (SMOW), involves using condensed water of gas fields and deposits of liquid hydrocarbons as production material and heavy water is extracted directly from underground water during development and exploitation of gas fields and deposits of liquid hydrocarbons.

EFFECT: invention enable to obtain heavy water without special enrichment directly during extraction, which reduces consumption of material, production power consumption and expenses on production equipment.

Description

The invention relates to the production of water, namely heavy water-D ₂ , and can find application in the extractive industry, in chemical production, as well as in industries of the fuel and energy complex.

Heavy water-D ₂ (deuterium oxide - D ₂ O, HDO) is an isotopic type of water in which a light hydrogen atom is protium (a stable hydrogen isotope containing one proton in the nucleus, denoted by ¹ H or H) - is replaced by its heavy isotope - deuterium (stable isotope, the nucleus contains one proton and one neutron, denoted as ² N or D).

Heavy water and any other deuterium compound in which the ratio of deuterium to hydrogen atoms exceeds 1: 5000 (Definition of terms on the list of nuclear materials, equipment, special non-nuclear materials and related technologies that are subject to export control. Appendix 7 to the order of the State Customs Committee of Russia dated 24.12. 2001 No. 1226 of the Decree of the President of the Russian Federation of February 14, 1996 No. 202 (as amended by the Decree of the President of the Russian Federation of June 21, 2000 No. 1151).

The isotopic composition of hydrogen in water is expressed by the ratio of the content of the heavy isotope to light (D / H) or light to heavy (H / D). In international practice, the generally accepted form for expressing the isotopic composition of hydrogen in a substance is δD, which is defined as the deviation of the isotopic composition of hydrogen of the studied substance from the isotopic composition of hydrogen of a substance taken as a standard:

δD = (R _sample / R _standard -1) · 1000 ‰,

where R of the _sample is the ratio of deuterium to protium (D / H) in the sample, and R of the _standard is the same ratio in the standard. In isotope studies, the SMOW standard (Standard Mean Ocean Water) was adopted as the standard, δD of which is assumed to be zero and denoted as δD = 0 ‰ (SMOW).

Heavy water of varying degrees of enrichment with its D ₂ O is used in chemistry, biology, hydrology, as an isotope indicator or tracer, in electronics, as a medium for growing large and highly pure single crystals, and also in nuclear physics, as an initial product for producing deuterium. Mostly and in large quantities, heavy water is used in energy, as a coolant and neutron moderator in nuclear reactors.

In its pure (concentrated) form, heavy water was not found in nature. In natural waters, heavy water is contained in very low concentrations, with the ratio: 1 water molecule containing atom D per 6000 ÷ 11000 ordinary water molecules, which in units of δD is in the range from +50 to -420 ‰ (SMOW) (Ferronsky V. I., Polyakov V.A. Isotopy of the hydrosphere. - M .: Nauka, 1983, 280 p .; Seletsky Yu.B., Polyakov V.A., Yakubovsky A.V., Isaev N.V. Deuterium and oxygen 18 in groundwater (mass spectrometric studies) .- M .: Nedra, VSEGINGEO, 1973, 144 pp.). Of all natural waters, the water of precipitation and, accordingly, of ice at the North and South poles of the Earth is the most depleted in deuterium. The δD value of these waters reaches -420 ‰ (SMOW). Values of δD from 0 to + 50 ‰ (SMOW) were established as single observations in small atmospheric precipitations of African deserts. These waters have no practical significance in the production of heavy water. The most widespread on the continents are waters having a range of deuterium to protium ratios from 1: 6400 (surface waters of tropical countries) to 1: 8400 (territories of the Arctic), which corresponds to a range of δD values from -15 to -250 ‰ (SMOW). The surface waters of Russia have a predominantly light isotopic composition with a ratio of deuterium to protium from 1: 7000 to 1: 8400, which corresponds to a range of δD values from -90 to -250 ‰ (SMOW). Of all the natural waters available for industrial use, ocean water has the highest concentration of heavy water molecules: the D / H ratio here is 1: 6420.54, which corresponds to a δD value of 0 ‰ (SMOW).

Heavy water (D ₂ O) is obtained from ordinary natural water, the concentration of deuterium in which is low, in various ways of its concentration. Industrial methods for producing heavy water are multi-stage electrolysis of water, distillation of water and hydrogen, hydrogen distillation followed by its burning in oxygen, multi-stage isotopic exchange of ordinary water with hydrogen-containing liquids and gases (ammonia, hydrogen, etc.), as well as combinations of various methods (Production heavy water.Translated from English.Ed., Zelvensky Y.D. - Moscow: Publishing House of Foreign Literature, 1961, 520 p.). With all methods of producing heavy water, the technological principle of production is based on the use at any stage of the production cycle of the product obtained at the previous stage of enrichment.

Ocean water is sometimes used as a raw material for the production of heavy water, as it has unlimited reserves and, of all natural waters, has the heaviest isotopic composition of hydrogen. A negative point when using ocean water as a raw material is its high salinity, which makes it necessary to conduct distillation beforehand, a low concentration of deuterium, which requires the processing of a large amount of water, the complexity and high cost of delivering ocean water to processing enterprises.

Underground fresh (drinking) water, due to limited reserves and low deuterium content (lower D content than in ocean water), is not used for the production of heavy water. Underground salt (formation) water, including water from oil and gas fields, due to their contamination with mineral and organic compounds, their low deuterium content (D content is also lower here than in ocean water), the complexity of their extraction and processing, and limited reserves, as well as due to a decrease in reservoir pressure during their production, which negatively affects the efficiency of the development of oil and gas fields, are also not used for the production of heavy water.

A common disadvantage of the known methods for the production of heavy water is the high energy intensity of production, the dependence on related industries, the need to use a large amount of precious metals, namely platinum, used as a catalyst, the need to process a large amount of raw scarce raw materials, significant capital and operating costs and, as consequence, the high cost of the resulting product. So, to obtain 1 kg of heavy water for raw materials and technological support for production, up to 50 tons of ordinary water is used if it needs to be repeatedly evaporated and condensed. With all methods of producing heavy water, the largest amount of feedstock and the main energy expenditures for its production (more than 90%) are in the first stage of water enrichment with deuterium, because the deuterium content in the materials used as raw materials is very low.

The objective of the present invention is to obtain water with a high deuterium content exceeding the deuterium content in ocean water from waters previously not used for these purposes, namely from groundwater, recoverable during the development and operation of gas and hydrocarbon deposits. The technical result, to which the claimed invention is directed, consists in obtaining heavy water without its special enrichment directly during water production, in a method for its production, in which there is an increase in the concentration of deuterium in the extracted product in the process of its extraction. The technical result for obtaining heavy water with a high concentration of deuterium (with an excess of D / H = 1: 5000) with the traditional method of production is to reduce the cost of raw materials and energy for its production when using gas and hydrocarbon fields as condensation water, which allows to exclude from the traditional production cycle the first stage of enrichment with water deuterium and, accordingly, allows to reduce the consumption of primary raw materials and energy, as well as the cost of production equipment howling enrichment.

To achieve the technical result, the material for producing heavy water is not reservoir bottom water located in the aquifer below the gas-water and gas-oil contact, but underground condensation and underground residual water of gas and hydrocarbon deposits above this boundary. Condensation and residual water are produced in conjunction with the extraction of hydrogen-containing gas from the fields. With such a place and such a method of groundwater extraction, the condensation and residual water obtained from the production of wells is enriched with deuterium both in reservoir conditions and during the flow of water through the well strings and transport communications. At the same time, the underground residual and condensation waters in the process of their extraction are substantially depleted of salts and, unlike ocean water, do not require distillation.

The enrichment of condensation and residual water of gas deposits with deuterium when the water is in reservoir conditions and in the process of their extraction occurs as a result of isotope exchange reactions between water vapor and droplet condensation water with hydrogen-containing gases and liquids of oil and gas deposits.

Underground conditions, isotope exchange reactions are promoted by high reservoir pressure, which reduces the evaporation of formation water, and increased pressure of saturated steam of hydrogen-containing gases, compared with the pressure of saturated steam of water vapor in the gas cap of deposits, as well as a high degree of isotopic fractionation and isotopic equilibrium between water vapor and hydrogen-containing gases and liquid deposits due to the long time they are together. The indicated properties of water and gases and the conditions for their location lead to a decrease in the mass of water vapor in gas deposits relative to the mass of hydrogen-containing gas in deposits, as a result of which the water of gas deposits in the vapor phase comes into isotopic equilibrium with the prevailing mass of hydrogen-containing gas in the reservoir.

When gas and water vapor enter the wellbore and transport communications, water vapor condenses, and the isotopic exchange reactions indicated for reservoir conditions occur between hydrogen-containing gases and water in the liquid phase. At the same time, as the temperature of the gas-water mixture decreases, as it moves from the bottom to the wellhead and in transport routes, the degree of water enrichment with deuterium increases, because the coefficients of isotopic fractionation for these reactions at low temperatures increase. The balance of the substance of the gas-water mixture during its transportation remains the same, because only condensation and residual water from the gas reservoir enters the well string and transport communications.

Unlike condensation and residual water of gas deposits, the isotopic composition of hydrogen in waters located below gas-water and gas-oil contacts (bottom water bottom) cannot be balanced by the gases dissolved in them, due to the multiple prevalence of the bottom water mass over the mass of dissolved water in it gases. The isotopic composition of hydrogen in bottom water in any geological situation remains deuterium depleted and corresponds to the initial natural background.

In the absence of hydrogen-containing gases and liquids in gas deposits, hydrogen isotope exchange reactions can take place only between water vapor and its liquid phase. Since the partial pressure and saturated vapor pressure (p) of water vapor enriched in deuterium are lower than the saturated vapor pressure of isotope-light water molecules (pH ₂ ¹⁶ O is greater than pH ₂ ¹⁸ O is more pHDO is greater than pDDO), then in the process of isotope exchange reactions deuterium is concentrated in the liquid phase (residual water). In such a system, water vapors (condensation water of gas deposits), in contrast to the case with the presence of hydrogen-containing gases and liquids, deuterium, on the contrary, are depleted.

Thus, enrichment of natural waters with deuterium can occur only in reservoir conditions and in the gas-saturated part of the aquifer. A prerequisite for the enrichment of condensation and residual water with deuterium is the presence of hydrogen-containing liquids or gases in gas deposits.

Example

The formation bottom water of the productive horizon of the gas condensate field was selected, the gas reservoir of which contains mercaptans, hydrogen-containing gases and condensation and residual water from the gas reservoir of this field, which is simultaneously extracted with gases. The temperature at the bottom of the wells was 95-110 ° С, at the wellhead - 23-37 ° С. Water was taken on separators, after complete separation of the fractions of water, hydrogen-containing gases and liquids. The hydrogen isotopic composition of the resulting water was analyzed on a mass spectrometer. The isotopic composition of water hydrogen was measured by the compensation method relative to the international standard SMOW. The research results are shown in tables 1 and 2.

Table 1 The results of analyzes of the isotopic composition of hydrogen in the bottom of the bottom water of a gas condensate field sample temperature (° C) isotopic composition of hydrogen in water downhole at the wellhead δD, ‰ (SMOW) H / d formation bottom water, object 1 95 27 -10 6485.39 formation bottom water, object 2 98 thirty -twenty 6551.57 formation bottom water, object 3 110 29th -fifteen 6518.32 formation bottom water, facility 4 one hundred 28 -26 6591.94

table 2 The results of analyzes of the isotopic composition of hydrogen in the condensation residual water of a gas condensate field temperature (° C) Isotopic composition of hydrogen in water downhole at the wellhead δD, ‰ (SMOW) H / d condensation water, object 1 110 fifty +175 5464.29 condensation water, object 2 one hundred 28 +343 4780.75 condensation water, object 3 95 25 +520 4224.04 condensation water, object 4 110 38 +255 5115.97 condensation water, object 5 110 48 +130 5681.90 condensation water, object 6 110 34 +241 5173.69 condensation water, object 7 one hundred 27 +389 4622,42 condensation water, object 8 95 44 +200 5350.45 condensation water, object 9 110 38 +241 5173.69 condensation water, object 10 one hundred 38 +220 5,262.74 condensation water, object 11 95 36 +225 5,241.26 condensation water, object 12 110 42 +246 5152.92 condensation water, object 13 110 37 +255 5115.97 condensation water, object 14 110 35 +2300 1950

From the research results presented in the tables, it follows that the condensation and residual waters of the productive horizon of the field simultaneously extracted with gas are significantly enriched in deuterium relative to the bottom waters of the productive horizon. It can also be seen from the obtained data that the isotopic composition of hydrogen in the condensation and residual waters produced simultaneously with gas at D / H ratios ranging from 1: 5681.90 to 1: 1950, which corresponds to a range of δD values from +130 to + 2300 ‰ (SMOW), significantly exceeds the deuterium content in ocean water, the D / H ratio in which is 1: 6420.54, which corresponds to the value δD = 0 ‰ (SMOW). Thus, when condensation water is extracted from gas deposits of fields, it is possible to obtain water along with deuterium content exceeding the deuterium content in ocean water without special enrichment.

Some industries require heavy water with a deuterium concentration in excess of D / H 1: 5000. In the traditional multi-stage production cycle of heavy water, water with such a deuterium content is obtained at the most energy-intensive first stage of enrichment of ordinary natural water, which requires the consumption of large amounts of ordinary water, high energy costs and metal-intensive equipment (Production of heavy water. Translation from English. Ed. By Zelvensky Y .D. - M.: Publishing House of Foreign Literature, 1961, 520 p.). From the data given in table 2, it can be seen that the concentration of deuterium in the condensation waters of hydrocarbon deposits can reach 1: 1950, i.e. significantly exceed the value of D / H 1: 5000. Thus, the use of condensation water from gas and hydrocarbon deposits as a raw material for the production of heavy water with a high concentration of deuterium allows us to exclude the initial stage of natural water enrichment from the production cycle.

Claims (1)

A method for producing heavy-D ₂ water, consisting of deuterium oxide (D ₂ O, HDO), with a total deuterium content exceeding the deuterium content in ocean water and characterized by a ratio of deuterium to protium D / H from 1: 6420.54 to 1: 1950, which corresponds to the range of δD values from 0 to + 2300 ‰ according to the standard of “mid-ocean water” of SMOW water, which uses condensation water from gas fields and liquid hydrocarbon fields as its material for production, and heavy water is extracted directly from groundwater during development and exploitation of gas and liquid hydrocarbon deposits.